Chimpanzee losses and successes.
Matthew W. Mitchell of Pennsylvanias Drexel University and the State University of New York, US, is the lead author of one chimpanzee paper that sheds light on the terrible situation in their African habitats. But with large numbers of Africas endemic species in the Gulf of Guinea and Congo Basin, this is not only about great apes, but also the rich diversity of bird, mammal, amphibian and retile that emerge from the Central African forest. Paul R Sesink Clee from Drexel and the University at Albany, US, is the lead in another paper on how habitat variation may lose us the chimpanzee populations from at least some of the habitats investigated here.
Matthews study looks at the effects of local factors on the generation of genetic differentiation in these awesome plant and animal species. In the Pleistocene, the forests became a refuge and cradle for primate and other speciations. One river (the Sanaga) separates the ellioti and troglogdytes subspecies of Pan troglodytes. This makes it the border also between central and eastern chimpanzees such as the latter and the western subspecies (Pt.verus and Pt.ellioti.) Looking at the genotypes of 604 chimpanzees, there are 2 or 3 distinct populations that probably split apart as long as 250,000 years ago. The 3rd population is one of the ellioti groups that split from each other in the forests of Cameroon and eastern Nigeria only around 4,000 years ago.
These 3 distinct populations are major parts of the widely distributed chimpanzee of sub-Saharan Africa. They inhabit rainforest here, but savanna and mixed habitats such as the central Cameroon woodland/savanna/ riparian forest zone are also used extensively. Their genetics has rarely been investigated. With the latest techniques much can be gleaned from the remaining wild animals about their recent history, migration, and relationships. The south of Cameroon is the furthest extent of the central/eastern subspecies of troglodytes and schweinfurthii. For more on the eastern subspecies, we have a very useful article in
Save the Congo Chimpanzee. The early separation of the 4 subspecies means they have differing patterns of population growth and decline throughout their long history. Interbreeding seems to have been possible at times, but very limited.
Using faeces and hair samples, technology now reveals population details that were impossible to investigate just a few years ago. mtDNA haplotypes and microsatellite genotype profiles may sound forbidding but the ease of their use leads to genomes of these subspecies that reveal a lot of their history. As expected, the 2 of the distinct haplotypes seemed to apply to ellioti and troglodytes which overlap slightly. The so-called ecotone region of central Cameroon has been the site of some migration from one group to another subspecies. This may be the cause of 2 ellioti
Pauls study is named Chimpanzee population structure in Cameroon and Nigeria is associated with habitat variation that may be lost under climate change. In combination with many researchers from the Wildlife Conservation Society, the Universities of Stirling, New Orleans, and Université Montpelier as well as the Zoological Society of San Diego and the Ebo Forest Research Project in Yaoundé, he investigates habitat loss/climate change and its effect on the primates populations. The ENMs or ecological niche models they have created for 3 chimpanzee populations fit the 2 ellioti and the troglodytes
If these habitats change, the chimpanzees most likely to be affected would appear to be the central Cameroon population of Pan troglodytes ellioti The ENMs for 2020, 2050 and 2080 project a concerning and progressive reduction in the niche for them. Reduced forest cover is one of many problems for them. Moist rainforests on the other hand seem to be able to survive current global warming scenarios, along with their primate residents. This isolation by environment among Cameroon/Nigerian chimpanzees has led to one half of them being in a fundamentally different and very threatened niche. Other niches threatened near the Sanaga River could be those of Mandrillus spp and at least 6 species of Cercopithecus. Obviously, if the apes have different niches that arent directly connected to this geographical barrier, the other primates might well also have habitat/niche preferences. We already have evidence that insects, reptiles and bird species have a pronounced ecological gradient across Cameroon. As rainfall patterns change dramatically, 30% of all species could become extinct, with the Amphibia most likely to be lost.
Now it remains to be seen of the chimpanzee will adapt to new conditions in their habitat. With completely different ENMs, the chimpanzee populations could be unable to adapt any part of their niche to resemble those of their relatives. Logging and hunting are the terrible danger at the moment, but by 2080, we cant expect the habitat to provide any suitable niche in central Cameroon.